/Engine/Plugins/NetcodeUnitTest/NetcodeUnitTest/Source/NetcodeUnitTest/Public/UI/SLogWindow.h
Setup a multicast version of the standard OnWindowClosed delegate
typedef TMulticastDelegate_OneParam< void, const [TSharedRef](API\Runtime\Core\Templates\TSharedRef)< [SWindow](API\Runtime\SlateCore\Widgets\SWindow) > & > FMultiOnWindowClosed